The present invention relates to a composition for controlling pathogenic bacteria and/or fungi on plants, trees and the like, in addition to a method wherein the composition is applied.
There exist different types of pesticides against organisms such as bacteria and fungi. These are often synthetic agents with possible drawbacks for humans, animals and environment. These agents moreover often have the drawback that the organism for controlling becomes resistant to the agent. A new agent must then be found for controlling the relevant pathogen.
It is further known of some fungicides that their activity is linked to temperature or that their activity depends on a determined degree of humidity. For treating plants and trees, which grow in the open air, such limited conditions of use are a great drawback. But similar problems can also occur in the case of crops cultivated in greenhouses.
The object of the present invention is therefore to provide a new pesticide which does not have the above stated drawbacks and which can be used to control pathogenic bacteria and fungi on plants, trees and the bike in situ.
This object is achieved according to the invention with a composition comprising lactoperoxidase, thiocyanate (SCNxe2x88x92) and/or iodide (Ixe2x88x92) and a hydrogen peroxide donor system, in particular glucose oxidase and glucose. In addition to the glucose oxidase/glucose system other hydrogen donor systems can also be used such as sodium percarbonate or stabilized hydrogen peroxide.
An advantage of this new agent according to the invention is that the danger of resistances is very small or even absent. Moreover it is an agent on a natural basis.
The antimicrobial activity of lactoperoxidase is per se known and described for instance in European patent no. 0 514 417 and international application WO97/26908. These relate however to application of this so-called LP system (lactoperoxidase system) for conserving cosmetic products or for medical purposes in humans and animals. Because the treatment of microbial infections in plants, trees and parts thereof takes place under entirely different (and often greatly varying) conditions than in humans and animals, it is not obvious that known systems based on lactoperoxidase could also have an in situ biocidal effect on plant pathogens.
As already indicated above, many plants, particularly agricultural crops, and trees grow in the open air and are thereby subjected to weather conditions such as wind, rain, sunshine, changing temperatures and the like. All these factors can reduce the effectiveness of a system which is based on enzymes, which are after all relatively sensitive as compared to chemical pesticides. A skilled person in the field of pesticides will hereby not immediately appreciate the usefulness and wide applicability of a pesticide based on lactoperoxidase.
In a preferred embodiment of the present invention an oil base is also added to the composition. By including a relatively small quantity of an oil base in the composition the effectiveness of the composition is further improved in surprising manner.
The oil has the object of ensuring a good distribution of the composition on the leaves and other parts of the plant and of preventing evaporation of the agent, which is in fact an aqueous composition. The activity of the composition does not depend on a specific temperature or relative humidity. The chance of resistance to the composition being developed is small, because the system has no specific effect on micro-organisms, such as antibiotics do have. Plants, animal and human cells are insensitive to the system.
The composition according to the invention comprises for instance per liter of aqueous solution at least 10 mg lactoperoxidase; at least 50 I.E. glucose oxidase; at least 0.05% glucose; at least 25 mg iodide (Ixe2x88x92), at least 5 mg thiocyanate (SCNxe2x88x92); and optionally a maximum of 1 v/v % oil base. A maximum of 0.2 v/v % spreading agent can optionally further be present. The composition preferably comprises per liter of aqueous solution at least 50 mg lactoperoxidase; at least 100 I.E. glucose oxidase; at least 0.1 w/v % glucose; at least 50 mg iodide (Ixe2x88x92); at least 10 mg thiocyanate (SCNxe2x88x92) and optionally a maximum of 0.1 v/v % oil base. A maximum of 0. 1% spreading agent can optionally further be present.
A good activity of the composition is obtained when it comprises per liter of aqueous solution 10-100 mg, preferably 30-70 mg lactoperoxidase; 50-1000 I.E., preferably 100-250 I.E. glucose oxidase; 0.05-2 w/v %, preferably 0.1-1 w/v % glucose; 25-200 mg, preferably 50-100 mg iodide (Ixe2x88x92); 5-50 mg, preferably 10-20 mg thiocyanate(SCNxe2x88x92) and optionally 0.1-2 v/v %, preferably 0.2-1 v/v % oil base. The quantity of spreading agent which may optionally be added amounts to 0.01-0.2 v/v %, preferably 0.05-0.07 v/v %.
The oil base always consists of at least an oil and an agent for emulsifying the oil in the aqueous solution to form an oil-in-water emulsion. This agent for emulsifying can be a separate emulsifier but can also be formed by the oil itself, which has self-emulsifying properties. Such self-emulsifying oils can be manufactured by modifying oil, for instance by ethoxylating. On the basis of his professional knowledge the skilled person can select the most suitable emulsifier for a determined oil.
The oil used in the oil base is chosen from the group of mineral oils, vegetable oils, animal oils or is a mixture of one or more oils from one or more of these groups. Recommended are oils which inherently already have a greater or lesser degree of antimicrobial activity.
Examples of vegetable oils are peanut oil, sesame oil, rape-seed oil, linseed oil, castor oil, soybean oil, corn germ oil, cotton-seed oil. Of these peanut oil is found to be particularly suitable for the purpose of the invention.
In the case of an animal oil, for instance fish oil such as herring oil or mackerel oil is chosen. Suitable mineral oils are for instance diverse types of paraffin oil or kerosine-type oils.
In order to further facilitate the distribution of the composition over the surface for treating, one or more spreading agents can further be added to the composition or the oil base. A skilled person in this field is very well capable of selecting suitable spreading agents. Such spreading agents are usually non-ionogenic surface tension-reducing substances. Recommended are ethoxylated alcohols, for instance Volpo T7(trademark), and phosphatidyl lipids, such as Nathin 130(trademark).
In a particularly suitable embodiment of the composition according to the invention, the oil base consists of at least 80-90, preferably 85 parts oil; 5-15, preferably 10 parts emulsifier; optionally 1-10, preferably 5 parts of a lecithin fraction. Optionally 0.01-0.2 v/v %, preferably 0.05 v/v % spreading agent can be added to the composition per liter of aqueous solution.
In a preferred embodiment the composition according to the invention comprises an oil base consisting of peanut oil, a polyoxyethylene sorbitol hexaoleate, such as the emulsifier Atlas 1086(trademark) (ICI) and a lecithin fraction consisting of phosphatidyl lipids, such as Nathin 130(trademark) (ENR), in addition to a spreading agent consisting of ethoxylated alcohols, such as Volpo T7(trademark) (CRODA).
In order to prolong the activity of the composition in situ, one or more adhesives can be added. Adhesives ensure for instance that the constituents of the composition are not rinsed off the plant by rain or other conditions. Adhesives can also be selected in simple manner by a skilled person in this field from the available supply. Examples are starch, gums such as xanthan gum, gum Arabic and carboxymethyl celluloses (CMCs).
The composition can be applied by means of spraying, sprinkling, atomizing, overhead spraying, watering, immersing, drip irrigation. A particularly advantageous method for applying the composition is spraying both by means of low volume methods (mist systems) and high volume methods. Drip irrigation can be used for culture systems on rockwool and other growth substrates. The agent according to the invention can also be used to disinfect drip irrigation systems. In both latter cases the presence of the oil base is not strictly necessary for an optimal activity. Immersion in a bath with the composition is particularly suitable for the treatment of plant parts, in particular harvestable parts, such as bulbs, tubers, fruits and the like.
The composition according to the invention can be made commercially available in different forms. A form is recommended wherein the activity of the enzyme lactoperoxidase is delayed as long as possible because this increases the shelf-life of the product. The activity of the enzyme lactoperoxidase starts as soon as a hydrogen peroxide donor is present. In the present case the glucose oxidase/glucose system is the hydrogen peroxide donor. It is therefore recommended, at least for determined applications, to supply the hydrogen peroxide donor separately of the enzyme lactoperoxidase. In addition, the oil base and the spreading agent can, if desired, also be packaged separately.
In a particular embodiment of the invention a kit is therefore provided for forming the composition, which kit comprises an optionally concentrated enzyme composition consisting of at least lactoperoxidase and optional additives, a hydrogen peroxide donor composition consisting of at least glucose oxidase and glucose, thiocyanate and/or iodide and optional other additives, and an oil composition consisting of at least oil, an optional emulsifier, optional spreading agents and optional other additives, wherein the three compositions must be mixed with each other before use in a ratio such that a composition according to the invention is obtained.
The composition according to the invention can optionally be marketed in a concentrated form which may or may not be dry. The final composition is then obtained by dilution or dissolving in for instance water.
Fungi which can be successfully controlled with the composition according to the invention are inter alia: Botryotinia spp (xe2x80x9cgrey mouldsxe2x80x9d), such as for instance B. fuckeliana (anamorphic Botrytis cinerea), Didymella spp, such as for instance D. bryonia (=Mycospherella in cucurbitaceae), D. lycopersici (=cancer in tomato), Puccunia spp (xe2x80x9crustsxe2x80x9d), such as for instance P. horiana (=Japanese rust), Sphaerotheca spp (xe2x80x9ctrue mildewxe2x80x9d), such as for instance S. fuliginea (mildew in cucumber) and S. pannose (mildew in rose), Erysiphe spp, Oidium spp and Leveillula taurica (also true mildew types), Fusarium spp (xe2x80x9cfoot rot and/or wilt diseasexe2x80x9d), Phytophtora spp (xe2x80x9cfoot and/or root diseasexe2x80x9d), Pythium spp (xe2x80x9cfoot diseasexe2x80x9d), Plasmopara, Peronospora, and Sclerospora spp (the downy mildew types), Rhizoctonia, Verticillium and Sclerotinia spp (causes of spot), Rhizopus and Penicillium spp (causes of (storage)rot) and Venturia spp (causes of scab).
Bacterial infections which can be treated with the composition according to the invention are inter alia infections by Erwinia chrysanthemi, Pseudomonas syringae, Xanthomonas campestris, Curtobactrium flaccumfaciens. 
The composition and the method according to the invention can be used in the broadest sense for plant protection and pathogen control in for instance agriculture, horticulture, vegetable growing, ornamental plant cultivation, fruit growing, bulb growing, the culture of potted plants, forestry etc., and as consumer product for indoor plants. In addition to the plants and trees themselves, plant parts can also be treated such as bulbs, tubers, flowers, cuttings, fruits and the like.
Plant protection and pathogen control are understood to mean according to the invention both preventive and curative activities. In most cases however this will relate to the killing of pathogens which are already present. In a number of other cases however, preventive treatment of plant parts can also be envisaged. The composition according to the invention requires free water to be active, but can be made active again after being dried by adding water.
The composition according to the invention is a natural pesticide and therefore environmentally-friendly.
The invention further relates to a method for controlling plant-pathogenic bacteria and/or fungi on plants, trees and parts thereof, comprising of applying the composition according to the invention to the plant, tree or part thereof.
The invention will be further elucidated with reference to the following examples, which are only given by way of illustration.